Abstract : This paper considers the feasibility of incorporating research results from cognitive science into the modeling of performance on psychometric tests and the construction of test items. The paper focuses on the feasibility of modeling performance on a three-dimensional rotation task within the context of Item Response Theory (IRT). Three-dimensional items were chosen because there is a rich literature on the mental models that are used in their solution. To test the feasibility of psychometrically modeling performance on this item type an 80-item, three-dimensional rotation test was constructed. An inexpensive computer system was also developed to administer the test and record performance, including response-time data. Data were collected on high school juniors and seniors. As expected angular disparity was a potent determinant of item difficulty. The applicability of IRT to these data was investigated by dichotomizing response time at several points and applying standard item parameter estimation procedures. It was concluded that an approach to psychometric modeling that explicitly incorporates information on the mental models examiners use in solving an item is not only workable, but also essential for future developments in psychometrics.